DNA can be damaged by very low-energy radiation: How safe are 'eye-safe' lasers?

March 14th, 2014

That energetic particles damage DNA is not surprising. It is now appears that very low-energy OH radicals also damage DNA, with a propensity that depends on how vigorously OH rotates: rotationally 'hot' OH induce irreparable double breaks. These findings utilize OH formed in plasma created when intense IR femtosecond laser pulses propagate in water containing DNA. Industry characterizes as 'eye-safe' IR lasers. With such wavelengths being proficient at inducing DNA damage, how safe is 'eye-safe'?

Damage to DNA by high energy radiation constitutes the most lethal damage occurring at the cellular level. Surprisingly, very low-energy interactions - with OH radicals, for instance - can also induce DNA damage, including double strand breaks. It is known that single strand breaks in the DNA backbone are amenable to repair but most double strand breaks are irreparable. The propensity with which slow OH radicals damage DNA depends on their rotational energy: rotationally "hot" OH is more proficient in causing double breaks. These novel findings are from experiments conducted on DNA in a physiological environment. Intense femtosecond laser pulses are propagated through water (in which DNA plasmids are suspended), creating plasma channels within water, resulting in generation, in situ, of electrons and OH radicals. It is shown that use of long laser wavelength light (1350 nm and 2200 nm) ensures only OH-induced damage to DNA is accessed. It is noteworthy that industry presently characterizes as "eye-safe" lasers that emit at wavelengths longer than 1300 nm.

But it is such wavelengths that are proficient at inducing damage to DNA: how safe is "eye-safe" when DNA in the eye can be readily damaged?

Provided by Tata Institute of Fundamental Research

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